Rotary blower with abrading rotor ends and abradable casing sealing ridges



Dec., 2?, @949 R, p. MccULLocl-x ET AL, 2,492,935

v ROTARY BLOWER WITH ABRADING ROTOR ENDS AND ABRADABLE CASING SEALINGRIDGES Filed Nov. 22, 194s Patented Dec. 27, 1949 l ROTARY BLOWER WITHABRADING ROTOR ENDS AND ABRADABLE CASING SEALING RIDGES Robert P.McCulloch, Fox Point, and John L.

Ryde,

Milwaukee, Wis., assignors, by mesne assignments, to Borg-WarnerCorporation, Chicago, Ill., a corporation of Illinois ApplicationNovember 22, 1943, Serial No. 511,250

25 Claims. 1

This application is a continuation-impart of the co-pending originalapplication of Robert P. McCulloch and John L. Ryde, for a Rotaryblower, led March 20, 1942, Serial No. 435,506, now issued as Patent No.2,393,116, dated January 15, 1946.

This invention relates to rotary or positive displacement blowers orsuperchargers of the type used on Diesel engines to provide forced airinduction and scavenging.

Such blowers comprise a pair .of rotors having intermeshing lobesrotating in an appropriate housing or casing. The air or other Iiuidbeing pumped is trapped in the pockets between the lobes and the sidewalls of the casing and advanced from the inlet to the outlet.Consequently a pressure diiferential obtains between the inlet andoutlet.

This pressure differential tends to cause leakage around the ends of therotors, and notwithstanding the various renements which have beenincorporated in the design of these blowers, the leakage past the endsof the rotors constituted a serious limitation to their eiciency.

Heretofore this leakage was accepted as inherent and inevitable, foralthough the machining of the parts was conducted with the greatestaccuracy, production tolerances had to be maintained. In addition,expansion clearance had to be provided. This follows from the fact thatwhile the rotors and casings may be made of metal having the samecoemcients of expansion and contraction, a load suddenly applied on acold blower would result in rapid expansion of the rotors well inadvance of any equivalent expansion on the part of the casing orhousing.

Thus, unless adequate clearance existed between the ends of the rotorsand the adjacent end walls of the casing or housing the rotors wouldbind and ruin the machine.

Prior to this invention, nothing Vwas done tov reduce this clearance foras stated hereinbefore, its presence was regarded as an inherent andinevitable characteristic of this type of machine. The presentinvention, however, does contemplate the provision of means to reducethe leakage past the ends f the rotors to an inappreciable minimum.

To this end, it is an object of this invention to provide sealing meansso designed and constructed that it may be incorporated in blowers ofthis type without danger of having the rotors bind and without danger ofpitting or scoring the surfaces of the end walls or the ends of therotors.

provision of novel sealing means carried by the end plates or walls andso designed and constructed as to accommodate itself to the particularinstallation and automatically maintain a minimum clearance between theends of the rotors and the adjacent end walls.

Another object of this invention is to provide sealing means for thepurpose described which may be quickly and easily replaced.

A further object of this invention is to provide sealing means for thepurpose described which is carried by the end walls or closure plates ofthe housing and which presents a multiplicity of projections or thinedges to the adjacent ends of the rotors to automatically accommodatethe seal to the installation without danger of scoring, pitting orotherwise injuring the rotors or any part of the blower. In thisconnection one portion of the sealing means embodies a plurality ofarcuate or circular spaced ridges on the housing end walls, the radii ofthe circles defining these annular ridges being at the axes of the rotorshafts to provide concentric elements. Another portion of the sealingmeans comprises a plurality of radially disposed ridges that intersector cross the concentric ridges and porvide therewith a multiplicity ofuniformly disposed flat bottomed depressions or recesses, sucharrangement presenting a gridiron or waffle pattern that is co-extensivewith the area on the end walls that is traversed or swept by the ends ofthe rotors when the blower is in operation.

It is another object to provide a combination in which the rotor ends,sweeping across the sealing element, are deliberately roughened orprovided with abrading means or serrations whereby any rotating contactof the end of the rotor with said sealing means causes an abradingaction on said sealing means whereby portions of the latter are removedor worn away and an optimum working clearance is maintained.

With the above and other objects in view which will appear as thedescription proceeds, this invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed, and more particularly Another object of this inventionresides in the defined by the appended claims, it being understood thatsuch changes in the precise embodiment of the hereindisclosed inventionmay be made as come within the scope of the claims.

The accompanying drawing illustrates a complete example of a physicalembodiment of the invention constructed in accordance with the bestinode so far devised for the practical application of the principlesthereof, and in which:

Fig. 1 is an end view of a blower embodyins this invention, the end wallor coverrplate thereof being broken away:

Fig. 2 is an enlarged sectional view taken through part of Fig. 1 on theplane of line 2-2 thereon; and

Fig. 3 is a view similar to Fig. 2 showing a modification thereof.A

Referring now particularly to theaccompanying drawings, in which likenumerals indicate like parts, the numeral 5 designates the casing orhousing of a. rotary or positive displacement type blower, the oppositeside walls of which have an inlet 6 and an outlet 1 therein. 'I'he endsof the casing are closed by at end walls 8 bolted or otherwise securedthereto. vThese end walls carry bearings not shown in which the shafts 9ofrotors i0 rotate.

The rotors I0 are geared together by suitable gears (not shown) xed totheir shafts, and have intermeshing lobes Il which sweep across theinner surfaces of the casing side walls and coact therewith to formpockets l2 in which the air or other fluid being pumped is entrapped andcarried from the inlet to the outlet. Obvious1y, therefore, during theoperation of the blower a pressure differential obtains between theinlet and outlet.

'I'his pressure differential in previous constructions causes leakagearound the ends of the rotors, that is, between the ends of the rotorsand the adjacent i'at inner surfaces of the end walls 8.

It is desirable that a minimum clearance or substantial seal existbetween the ends of the rotor lobesI Il and the housing end -walls 8,for the purpose of materially reducing the leakage, and for this reasonthe construction contemplated herein may be used to advantage.

A substantial seal is effected by means of the instrumentlities shownherein. In this construction the lobes of the rotors may be hollow andpreferably the end surfaces thereof are provided with serrations orsubstantially sharp cutting projections or abrading means 30, as will beclearly apparent in Figs. 1 and 2. As illustrated, each lobe I lpresents a substantially cylindrical portionto the rotor housing, andthe end surfaces of the lobes are circularly grooved to provide aplurality of sharp arcuate ridges or projections disposed substantiallyconcentric with the axis of the cylindrical portions of the lobes. Anyabrading surface such as a grit-blasted surface is feasible, the purposeof said abrading surface on the ends of said rotors being apparent fromlater description herein.

The sealing means herein disclosed consists of a multiplicity ofprojections or tiny ridges 21 formed on the end walls l8 and coveringthe areas thereof that are presented to the sweeps of the rotors. Thesetiny ridges 21 are formed of rubber or synthetic rubber that isvulcanized or bonded as a thin sheet or liner to the inner surfaces oftne end walls as shown in Fig. 2, or imbedded in shallow recesses in thesurfaces of said end walls as shown in Fig. 3, the said ridgesprojecting a slight distance out from the surface of the sheet proper.These sealing areas, as shown in Fig. 1 comprise a plurality ofconcentric arcuate or circular ridges that are spaced from each other,the curves thereof being struck from radii at the axes of the rotorshafts 9. The liner, of course, has openings (not shown) through whichthe shafts 9 extend. Intersecting these arcuate ridges there is aplurality of radially disposed ridges. This disposition provides amultiplicity of uni- 4 formly disposed shallow depressions or recessesof substantiallyl frusto-sectoral configuration bounded by theintersecting'circular and radial ridges, said depressions or recessesserving as static air pockets to increase the sealing effect. Thearrangement disclosed presents a gridiron or wallie pattern having thegeneral configuration of the numeral 8 and coextensive with the areas onthe end walls that are traversed by the ends of the rotors duringrotation of the latter.

It is desirable that the radial dimension of the metal forming the wallat the edges of the rotor ends be such that the wall will at all timesspan the space between any two adjacent ridges 21, whereby air isprevented from by-passing the end of the rotor as lt swings past oneridge toward another.

In actual practice on one size of device the liner sheet of rubber. orsynthetic rubber or other suitable resilient, pliable materials such asplastics, has a thickness of approximately ten thousandths (.010) of aninch and the ridges project upwardly or perpendlcularly therefrom twentyto twenty-five-thousandths (.020 to .025) of an inch, andthe edges orsummits of the ridges 21 presented to the ends of the rotors are but onesixty-fourth (l/g) of an inch wide. The ridges 21, as shown in Fig. 2,are spaced apart with a fiat'portion of the liner exposed therebetween,and decrease in width in a direction from the end wall 8 toward theadjacent end of the rotor, so that the ridges 21, being of substantialheight, can ex slightly as the rotor initially engages the Vsame androtates relatively thereto. As will be readily apparent, thisarrangement will produce an exceptionally effective seal without dangerof injury to the rotors or any other portion of the machine.

In operation, the rotors I0 are fitted into the housing 5 with not morethan a bare minimum oclearance from the end sealing means. As the deviceis run in through any operation or any process ofmanufacture, heat dueto the operation of the rotors I0 will expand them longitudinally towhere they may contact the end seal means. When this occurs, theresilient ridges 21 are initially deformed as the expanded rotors l0rotate, and upon additional longitudinal'expansion of the rotors I0 andpressural contact with the ridges 21, the ends of the rotors abrade awaya sufficient amount of the ridges 21 to allow the rotor to passthereover without substantial binding action. This creates, after ashort period of operation, the minimum clearance for normal operatingconditions. Should the device be operated at abnormal speeds, causingthe rotors to expand still more, further abrading action will occur andthe rotor will automatically provide the clearance required and willcontinue to operate instead ofseizing or sticking in the housing. Theadvantage of this is obvious.

In the event the material forming the seal is worn oil to an excessiveamount due to expansion of the rotor under abnormal operatingconditions, the cover plate of the housing may be removed and a newsealing means provided, or a new cover plate having proper sealing meansmay be substituted without much expense. It is thus seen that theeiciency of the blower may be brought up to a desired amount by acomparatively inexpensive substitution of parts. or by a simple repairjob.

While we have described our invention in connection with certain specicembodiments thereof, it is to be understood that this is by way ofillustration and not by way of limitation and the scope of our inventionis deiined solely by the appended claims which should be construed asbroadly as the prior art will permit.

We claim:

l. In a rotary blower of the type including a housing having an endwall, and a rotor of hard, substantially inexible material journaled insaid housing and having an end adjacent said end wall, a plurality cfridges of resilient pliable material disposed on the inner side of saidend wall of the housing and arranged to present a gridlike surface tosaid adjacent end of the rotor to provide an eifective seal between saidadjacent end of the rotor and said end wall of the housing, saidadjacent end of the rotor being provided with substantially sharp,abrading means capable of rapidly abrading the ridges upon rotatingcontact relative thereto, whereby an optimum working clearance ismaintained between said end wall of the housing and said adjacent end ofthe rotor.

2. A rotary blower according to claim 1, wherein the grid-like surfacecomprises a iirst plurality of spaced apart ridges and a secondplurality of spaced apart ridges intersecting the first plurality ofridges to dene a plurality of depressions, the open ends of whichdepressions face said adjacent end of the rotor.

3. A rotary blower according to claim 1, wherein the resilient ridgesare sufliciently high and have such resilience characteristics as to bedeformed upon initial rotating contact by the end of the rotor and havesuch durability characteristics as to be abraded by the rotor uponincreased pressural contact due to longitudinal expansion of the rotorrelative to the housing,

4. A rotary blower according to claim 1, wherein the ridge material isof sufficient height and has resilience and durability characteristicssuch that upon rotating contact of the rotor end surface with theridges, the ridges are initially distorted to accommodate slightrelative expansion of the rotor with respect to the housing, and thenupon increased expansion of the rotor the ridges are abraded by therotor end to reduce their height, the resilience of the ridge materialbeing such that the ridges tend to return to their original nondistortedcondition when rotating contact of the rotor therewith ceases, therebymaintaining an optimum sealing condition.

5. In a rotary blower of the type including a housing having an endwall, and a rotor of hard, substantially inflexible material journaledin said housing and having an end adjacent said end wall, a firstplurality of concentric spaced apart ridges, and a second plurality ofradially extending spaced apart ridges intersecting said concentricridges, said intersecting ridges being formed cf resilient, pliablematerial and being disposed on the inner side of said end wall of thehousing and defining a plurality of depressions of frustosectoralconfiguration with the open ends of the depressions facing said adjacentend of the rotor to provide an effective seal between said adjacent endof the rotor and said end wall of the housing, said adjacent end of therotor being provided with substantially sharp, abrading means capable ofrapidly abrading the ridges upon rotating contact relative thereto,whereby an optimum working clearance is maintained between said end wallof the housing and said adjacent end of the rotor.

6. In a rotary blower of the type including a housing having an endwall, and a rotor of hard,

substantially inexible material journaled in said housing and having anend adjacent said end wall, a plurality of ridges of resilient, pliablematerial disposed on the inner side of said end wall of the housing andarranged to present a gridlike surface to said adjacent end of the rotorto provide an effective seal between said adjacent end of the rotor andsaid end wall of the housing, said adjacent end of the rotor having thesurface thereof grooved to provide a plurality of sharp projectionscapable of rapidly abrading the ridges upon rotating contact relativethereto, whereby an optimum working clearance is malntained between saidend wall of the housing and said adjacent end of the rotor.

'7. In a rotary blower of the type including a housing having an endwall, and a rotor of hard, substantially inflexible material journaledin said housing and having an end adjacent said end wall, a plurality ofridges of resilient, pliable material of less hardness than the materialof the rotor disposed on the inner side of said end wall of the housingand arranged to present a grid-like surface to said adjacent end of therotor to provide an efcient seal between said adjacent end of the rotorand said end wall of the housing, said adjacent end of the rotor havinga surface deliberately roughened sufficiently with respect to theabrasion susceptibility of the ridge material to provide cutting meanssuch that the maximum rate of thermal expansion of the rotor in use doesnot exceed the rate at which the roughened end surface of therotor canremove the ridge material in contact therewith, whereby to maintainadequate working clearance.

8. In a rotary blower of the type including a housing having an endwall, and a rotor of hard, substantially inexible material journaled insaid housing and having an end adjacent said end wall, a plurality ofridges of resilient, pliable material disposed on the inner side of saidend wall of the housing and arranged to present a gridlike surface tosaid adjacent end of the rotor to provide an effective seal between saidadjacent end of the rotor and said end wall of the housing, the rotorcomprising a plurality of hollow lobes, the end of each lobe beingprovided with substantially sharp abrading means capable of rapidlyabrading the ridges upon rotating contact therewith, whereby an optimumworking clearance is maintained between said end wall of the housing andsaid adjacent end of the rotor.

9. A rotary blower according to claim 8, wherein the ridges decrease inwidth in a direction from the housing end wall toward the adjacent endof the rotor.

10. A rotary blower according to claim 8, wherein the grid-like surfaceis at least coextensive with the area of the end wall traversed by theend of the rotor during rotation of said rotor.

11. A blower according to claim 8, wherein the area of the grid-likesurface engageable by the rotor in the course of rotation substantiallyexceeds the area engaged by the end surface of the rotor at any oneinstant, thereby permitting cooling of the grid-like surface of the endwall and increasing its useful life.

l2. In a rotary blower of the type including a housing having an endwall, and a metallic rotor journaled in said housing and having an endadjacent said end wall, a plurality of spaced apart ridges of materialof less hardness than the ma- 76 terial of the rotor disposed on theinner side of said end wall of the housing and arranged to present agrid-like surface to said adjacent end of the rotor to provide aneffective seal between said adjacent end of the rotor and said end wallof the housing, the rotor comprising a plurality of hollow lobes, theend of each lobe being provided with substantially sharp abrading meanscapable of rapidly abrading the ridges upon rotating contact therewith,the walls of the hollow lobes having a minimum thickness greater thanthe maximum spacing between any two adjacent ridges on said end wall ofthe housing, whereby air is substantially prevented from by-passing saidadjacent end of the rotor as it sweeps past the ridges.

13. In a rotary blower of the type including a housing having a sidewall and an end wall, and a rotor of hard, substantially inflexiblematerial journaled in said housing and having an end adjacent said endwall, a plurality of ridges of material of less hardness than thematerial of the rotor disposed on the inner side of said end wall of thehousing and arranged to present a grid-like surface to said adjacent endof the rotor to provide an eiective seal between said adjacent end ofthe rotor and said end walll of the housing, the rotor comprising aplurality of hollow lobes each presenting a substantially cylindricalportion to the side wall of the housing, the end face of each lobe beingcircularly grooved to present substantially sharp projections to thegrid-like surface capable of rapidly abrading the ridges comprising saidgrid-like surface upon rotating contact therewith, whereby an optimumworking clearance is maintained between said end wall of the housing andsaid adjacent end of the rotor.

14. A rotary blower according to claim 13, wherein the grooves aresubstantially concentric about the axis of the substantially cylindricalportions of the rotor lobes.

l5. A rotary blower according to claim 13, wherein the substantiallysharp projections comprise a plurality of substantially concentricridges arranged substantially closer together thanthe ridges on the endwall of the housing.

16. In a rotary blower of the type including a housing having an endwall, and a rotor of hard, substantially inflexible material journaledin the housing and having an end adjacent said end wall, a liner havinga plurality of ridges of resilient, pliable material disposed on theinner side of said end wall of the housing with the ridges intersectingeach other to define a plurality of depressions therebetween formingstatic air chambers, the ridges presenting a grid-like surface to saidadjacent end of the rotor to provide an effective seal between saidadjacent end of the rotor and said end wall of the housing, and saidadjacent end of the rotor being provided with substantially sharpabrading means capable of rapidly abrading the ridges upon contacttherewith and relative rotation with respect thereto to maintain anoptimum working clearance between said end wall of the housing and saidadjacent end of the rotor.

17. A rotary blower, comprising: a housing having end walls; a pair ofmeshing, metallic rotors in the housing between the end walls, saidrotors having the ends thereof disposed adjacent the end walls of thehousing; and a liner having a plurality of ridges of resilient, pliablematerial disposed on the inner side of each ofthe end walls of thehousing. the ridges on each liner intersecting each other to present agrid-like surface 8 to the adjacent ends of the rotors to thus form aneffective seal between the ends of the rotors and the end walls of thehousing, each of the ends of the rotors being provided with serrationscapable of rapidly abrading the ridges upon contact therewith androtation relative thereto, to thereby provide optimum working clearancebetween the end walls of the housing and the ends of the rotors.

18. In a rotary blower of the type including a housing having an endwall, and a rotor of hard, substantially inflexible material journaledin the housing and having an end adjacent said end wall, a liner ofresilient, pliable material mounted on the interior of said end wall ofthe housing and having a thickness of about .010 of an inch and havingflexible ridges on the surface thereof adjacent said end of the rotorarranged in the form of a grid, the height of said ridges being about.020 to .025 of an inch, and the summits of the ridges beingapproximately 1/s4 of an inch in width, said adjacent end of the rotorhaving substantially sharp abrading means thereon capable of rapidlyabrading the ridges upon rotating contact relative thereto, whereby anoptimum working clearance between said end wall of the housing and saidadjacent end of the rotor is maintained.

19. A liner, for use in a rotary blower of the type including a housinghaving an end wall, and a rotor journaled in the housing with one end ofsaid rotor adjacent said end wall. comprising: a substantially at sheetof resilient, pliable material adapted to be mounted on the interior ofan end wall of the housing and to be engaged by and to form a seal withone end of the rotor, said sheet having a thickness of about .010 of aninch and having flexible spaced apart ridges on the surface thereofarranged in the form of a grid, the height l.of said ridges being about.020 to .025 of an inch, and the summit of the ridges beingapproximately 1/64 of an inch in Width.

20. A liner, for use in a rotary blower of the type including a housinghaving an end wall, and a rotor journaled in the housing with one end ofsaid rotor adjacent said end wall, comprising: a substantially at sheetof resilient, pliable material adapted to be mounted on the interior ofan end wall of the housing and to be engaged by and to form a seal withone end of the rotor, said sheet having exible ridges on the surfacethereof arranged in the form of a grid and including a series of spacedapart concentric ridges and a series of spaced vapart radial ridgesintersecting the concentric ridges.

21. A liner, for use in a rotary blower of the type including a housinghaving an end wall and a rotor journaled in the housing, comprising: asubstantially flat sheet of resilient, pliable material adapted to bemounted on the interior of the end wall of the housing and to be engagedby and to form a seal with one end of the rotor, said sheet having afirst plurality of spaced apart ridges on one side thereof and a secondplurality of spaced apart ridges on the same side thereof intersectingsaid rst plurality of rdiges, with the intersecting ridges extending ina direction substantially perpendicular to the plane of said sheet topresent a grid-like surface to the end of the rotor.

22. A liner, for use in a rotary blower of the type including a housinghaving an end wall and a pair of intermeshing rotors each having a shaftjournaled in the end wall, comprising: a substantially at sheetofresilient, pliable material adapted to be mounted on the interior of theend 9 wall o'f the housing and'tobe engaged by and to form a seal withone end of each of the rotors.

said sheet'having an opening 'thereinl for each rotor shaft and' havinga rst plurality of spaced apart ridges on one side thereof and. a secondplurality'of spaced apart ridges on the same side thereof intersectingsaid rst plurality of ridges to present a grid-like surface to the endsof the rotors.

23. A liner as dened in claim 22, wherein the configuration of the linersheet has the general v appearance of the numeral 8.v

24. In a rotary blower of the type including a housing having an endwail, and a rotor of hard,

substantially inexibie material journalled in said housing-and having anend adjacent said end wall, a plurality of projections of resilient,pliable material disposed on the inner side of said end wall of thehousing and arranged to present an abradable surface to said adjacentend of the rotor to provide an eiiective seal between said wdacent endof the rotor and said end wall of` the housing. said adjacent end of therotor being provided with substantially sharp, abrading means capable ofrapidly abrading the projections upon rotating contact relative thereto,whereby an optimum working clearance is maintained between said end wallof the housing and said adjacent end of the rotor.

25. A rotary blower according to claim 24 wherein the projections are ofsumcient height and have resilience and durability characteristics suchthat upon rotating contact ofthe rotor end surface with the projections,the projections are initially distorted to accommodate vslight relativeexpansion of the rotor with respect to the housing, and then 'upon`increased expansion of the rotor the projections are abraded by therotor end to reduce their height, the resilience of the projectionsbeing such that the projections tend to return to their originalnon-distorted condition when rotatingl contact of the rotor therewithceases, thereby maintaining an optimum sealing condition.

ROBERT P. MCCULLOCH vomi L. RYDE.

americas 'A The following-references aregoi recordv in the le of thispatent:

UNrrED STATES params i y nate

